Calamur Mahadevan FNA FASc FNASc FNI FISC FGS F.Pb.S FPSI MAIME FGMMSI (May 6, 1901 – 8 April 1962), sometimes known as C. Mahadevan, was an Indian specialist in economic geology, marine geology, and nuclear geology,^[1] and 1934 Founding Fellow of the Indian Academy of Sciences,^[1] elected for Earth and Planetary Sciences, serving on the Council of the Indian Academy of Sciences from 1948 until his 1962 death. Chosen as a Fulbright scholar, with aid from the United States National Research Council, he taught at the Massachusetts Institute of Technology.^[2] Appointed to the first Professorship of Geology at Andhra University after fourteen years as Superintendent Geologist at the Geological Survey of Hyderabad, he was known as a doyen or foundational figure in the field of Indian geology.^[3]

At Andhra University, where he was further appointed Principal, he introduced the subjects of Oceanography, Marine geology, Marine biology, Mineral processing, and Nuclear geology as firsts in India, which some scholars trace to his time at MIT.^[2]

He was a major contributor to the Geological and Mineralogical Research Committee of the Council of Scientific and Industrial Research,^[4] and to the Nuclear Research Board of the Atomic Energy Committee, of which his cousin-in-law, M. R. Srinivasan was Chairman.^[2] He was additionally UNESCO's designated Expert in Geology, in relation to which he spent 1956-7 in Brazil.^[5] The Mahadevan International Centre for Water Resources Management was named in his honour, as was the Calamur Mahadevan Endowment Lecture of the Geological Society of India.

He was born to Calamur Subrahmanya and C. Janaki, into the Calamur family, renowned for its scholarship,^[2] especially in Indian classics,^[6] and attended primary school in Buchireddypalem and in Madras, where he enrolled at Muthialpet High School. He earnt his M.A. in geology from the University of Madras in 1927 under Sir K. S. Krishnan, where his other teachers included T. N. Muthuswamy Iyer and M. O. P. Iyengar, and obtained his D.Sc. at the Indian Association for the Cultivation of Science under Sir C. V. Raman.

Mahadevan joined the Hyderabad State Geological Survey in 1931 as Assistant Superintendent, where he became a protege of Dr. Alexander M. Heron, recently retired as the Director of the Geological Survey of India.

As a Calamur, he was closely related to Sir C.V. Kumaraswami Sastri and Sir C. P. Ramaswami Iyer, among others.^[7][8] His sister Kanthammal Calamur married Dr. Cpt. Pennathur Krishnaswamy; their two daughters Saraswati and Kamakshi married Sir C.P.’s sons C. R. Pattabhiraman and C.R. Sundaram,^[9] whose respective granddaughter and son are Nanditha Krishna and C. Aryama Sundaram.

Mahadevan himself married Satyavati Rao, niece of V. N. Viswanatha Rao and Lakshmi Calamur Viravalli, daughter of Sir C. V. Kumaraswami Sastri. Satyavati's sister Lalitha and brother V. N. Krishna Rao both married Calamurs. Mahadevan's son Calamur Subrahmanyam, meanwhile married Lakshmi, daughter of C. R. Pattabhiraman and his first cousin Saraswati.